Telephone-exchange system



.Jan'. 1925- 1,522,905

L, POLINKOWSKY TELEPHONE EXCHANGE SYS TEM Fi Jan. 19, E52 4 Sheets-Sheet l o+79i+|0, Z

Jan. 13. 1925. 1,522,905,

' L. POLINKOWSKY TELEPHONE EXCHANGE SYSTEM Filed Jan. 19, 1922 4 Shefits-Sheet 2 1 2 2% 5 Ar 9H5 'hl//vibn [4'04 pofihkams/ry Jan, 13. 1925.

L. POLINKOWSKY TELEPHONE EXCHANGE SYS TEM Filed Jan. 19, 1922 4 she e-zs sheet 5 Mad pa/ih/roz m g gm as, i925.

- 1,522,905 POLINKOWSKY TELEPHONE EXCHANGE SYSTEM Filed Jan. 19, 1922 4 Sheets-Sheet 4 12H; N. if v 43/ hwn/or Z/pa pa/wkowsky scribers' line.

Patented Jan. 13, 1925.

Unit" LIPA POLINKOWSKY, OF ANTWER-P, BELGIUM, ASS-IGNOP. T0 WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N.- Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEI'II.

Application filed January 19, 1922.

T 0 all whom 2'25 may concern: I

Be it known that I, LIPA 'PoLrNKowsKY, a citizen of Russia, residing at let Rue de Bastion, Antwerp, Belgium, have invented certain new and useful Improvements in Telephone-Exchange Systems,- of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to systems employing machineswitc'hing apparatus for the establishment of talking connections The central ofiices, where the switching operations are performed in the extension and completion of connections between subscribers lines, serve not only their own respective areas in the exchange but also cooperate with each other in'disposing of calls receivedfor outlying areas. A call incoming to a given oiiice either from a local line or from a distant calling oflice maybe one of two general classes as regards its destination. It may in one case be intended for a local subscribers line, wherefore a group selector switch to which the connection is first extended, selects a local switch through which the call is routed to the loc'al sub- In the other instance the call may be destined'for a distant office, in which event the group selector, instead of choosing a local switch, selects an outgoing interofiice trunk to the distant called oflice, whereafter selective switches in said called ofiice are set to complete the connection.

The usual method is to controlthe automatic selective switches,.empl0yed for establishing local and interoflice connections as above outlined, by means of a sending device located at some convenient point near where the call originates. It may be a sender provided at the subscribers station or one located at the central oflice according to the character of the switches it controls. The control is exercised over a circuit which extends from the sender to the switches in succession as the connection progresses. As will be obvious, the length of this control circuit may vary between wide limits in systems such as those mentioned above where both local and interoiiice'service is given.

The object of this invention is to make provision for discriminating between the different classes of calls thatare extended Serial No. 530,244.

and to vary the character of the switch control circuits to suit theparticular call in- Volved.

A feature of the invention relates to an arrangement whereina selective switch, adapted to extend connections of different classes, is capable of detern'iining the classof any particular connectlon and to in turndetermine the preparation of the proper kind of a controllmg circuit for-governing the selective operations of the succeeding switches.

Such other features and advantages as are'contemplated by this invention will become-thoroughly understood from the following description and from the appended cl'aims.

In the drawing Figs. 1, 2, 3 and i when taken in proper order illustrate in detail a telephone exchange system of the character to which the principles of this invention are applicable.

Figs. 1, 2 and 4t when taken in order from left to right illustrate a connection establishedbetween a subscribers line in an orig inating ofiice and a subscribers line terminating locally in a-second or tandem office.

In Fig. 1 there is illustrated schematically to the left of the broken vertical line the first or originating oiiice in which a subscribersline terminates and also in which a register controlling sender is'loc'ated. To the right of the vertical broken lineis shown a first group selector switch located in the second or tandem ottice and in which the incoming trunk from the originating ottice terminates.

Fig. 2 shows a local second group selector switch in the tandem cities to which connections are extended through the terminal bank of the first group selector.

\ Fig. 4 shows a final selector switch located in the tandem office and which has access to local subscribers lines.

' Figs. 1, 3 and 4 when taken in the order named illustrate a connection established from the calling subsr-ribers line at the orig inating ofiice through the tandem oiiice and thence over an interoi'iice trunk line to a dist'ant oiiice to a called snbsrribcrs line.

In Fig. 3 the group selector switch there shown is one in which the interofiice trunk incoming from the tandem oiiice terminates. This group selector switch, which is located in the distant or called oiiice, has access to final switches such as the one shown in Fig. 4 which in turn have access to the called subscribers line.

It has been chosen to illustrate in this application a telephone exchange system in volving three central oflices. A subscriber in the first central otfice such as the subscriber of line 100 may establish a connection with a subscribers line in the second oflice and to do so he initiates the call in the regular way bringing about the association of the central office register sender 101 with his line. He then transmits the proper series of impulses to cause the registers of the sender 101 to take up settings corresponding to the designation of the wanted line. Two of these registers 104 and 105 are illustrated.

The register sender then becomes efiective to cause the selective operation of a group selector switch, the brushes of which are shown at 108 and 109, to choose a trunk line 110, 111 leading to the second oflice and there terminating in a first group selector switch 180. Following this operation the group selector switch 180 is controlled over the runk 110, 111 by the register sender in the originating office to select a trunk such as trunks 166, 167, 168 leading to local second group selector 230, shown in Fig. 2. Thereafter the second group selector switch 230 is selectively controlled to choose an idle final selector switch 440 in the group having access to the subscribers line 430 local to the second ofiice. Lastly, the final selector switch is operated to choose the called line.

Again the calling subscriber in the originating ofiice may establish a connection to a called subscribers line which belongs to a distant called ofiice accessible through the second ofiice, which in this case serves as the tandem point. In this event the calling subscriber initiates the call in substantially the same manner and causes the record of the wanted subscribers line to be registered on the register sender 101 in the originating office. Also in a similar manner the selector switch 108, 109 is controlled to extend the calling line to the first group selector switch 180 in the tandem office. At this point the operation differs inasmuch as the group selector switch 180 is now selectively controlled to choose an outgoing two-wire interofiice trunk such as the trunk 169, 170 leading to the distant called ofii'ce and there terminating in a group selector switch 330, indicated in Fig. 3. The group selector switch 330 is thereupon controlled over the extended connection from the register mechanism 101 to select an idle final switch similar to 140 which in turn is selectively controlled to complete theestablishment of the connection to the called subscribers line.

Inasmuch as the switch control circuit, which extends from the register sender 101 to the successive selector switches in the process of building up a connection,may vary considerably in its length, it'is advisable to make some provision for insuring the same degree of satisfactory operation when control is exercised over a long circuit as when the switch is being controlled over a comparatively short circuit. In the particular type of switch shown in this application the control of the selective movement is accomplished by the use of revertive impulses. operation and. by its movement causes impulses to be reverted over the control circuit back to the sender which receives the impulses and measures the permissible extent of operation of the switch in accordance with the registration of the sender. So far as the idea of insuring a satisfactory operation or the switch is concerned, the invention might equally as well be applied to systems of the character wherein impulses are sent directively to determine the. selective movement such as shown in the patent to (loodrum, No. 1,231,013, issued-June 26, 1917. In order to attain the desired result. the first group selector switch 180 in the second ofiice is adapted to distinguish, during its selective movement, between the calls of one class and calls of another class. If the selector switch 180 is operatedfto extend a connection over a local trunk to the second group selector switch 230 it determines this fact and accordingly prepares a fundamental control circuit which extends over aplain metallic path to the selector switch 280 whereby the register sender 101 may control this latter switch. However, should the group selector switch 180 be operated to select an interofiice trunk leading to the distant switch 330 it also determines this fact and prepares the incoming fundamental control circuit from the register sender and the outgoing fundamental control circuit to the distant switch 330 in such a manner that impulses reverted from the said switch 330 during its operation are repeated from the switch 180 back to the register sender 101. By means of this repeating fundamental cir cuit the impulses created at the switch and reverted back to the tandem office are reproduced at the tandem office and transmitted therefrom to the register sender 101, thus insuring a greater degree of accuracy in the control between the register sender and the distant selector switch.

The selector switches employed in this system are oi. the rotary power driven type in which a plurality of sets of brushes are provided and which are selectively tripped into operative engagement with the terminal bank during the rotation of the brush shaft. A switch of this general character is illustrated and described in the patent to M0 Berty No. 1,097,868, issued May 26, 191 1.

The selective switches are arranged to be That is to say the switch is set in controlled by a central office sender which consists of a plurality of sequence switch registers adapted to receive the designation impulses of a called line and to in turn ;ontrol the successive switches over a fundamental circuit in accordance with the regis trations on the registers. A register control device of the general character suitable for operation in connection with the system illustrated is shown. and described in my Patent No. 1,365,269, issued January 11, 1921.

The establishment of a local connection.

A description will now be given in detail of the operation of the system when connection is established between the subscribers line 100 in the originating oflice and a local subscribers line @130 terminating in the second office. The subscriber of line 100 upon initiating the call causes the operation of a line finder or line switch in the wellknown manner to extend his line through to the first group selector switch 108, 1.09 whereupon the register sender 101 is associated. The subscriber then transmits impulses over the line to set the successive registers 101, 105, etc. to record the designation of the called subscribers line cs0. Following this the brushes 108, 109 of the group selector are set under the control of the sender 101 on the terminals of the trunk line 110, 111 leading to the group selector switch 180 in the second office.

Upon the selection of the group selector switch 180 the fundamental circuit is estab lished from battery through the winding of relay 117, upper left contact 135 (1+1 back .ontact and middle ri ht armature of relay 112, conductor 111, brush 109, contact 107, armature and contact of relay 103, winding of the stepping relay 102, contact 171, contact 106, brush 108, conductor 110, upper contact 12ft (1-1-13), upper contact 128 (1+2), left back contact of relay 112 to ground. telay 117 becomes energized and closes the circuit from battery to the resistance 1 15, lower right contact 130 (la-5%), lower left contact 130 (1+17), winding of relay 115, left front contact of relay 117, upper right contact 172 (1) to ground. Also a circuit is closed from battery through the upper contact 133 (1+12), lower left contact 133 (bl-) windings of relay 11a, upper right contact 123 (id-1 lower left contact 123 (1+1 left front contact of relay 117 to ground through the contact 172. Relays 115 and us become energized and lock over circuits as above traced through the windings of said relays and thence to the lower left and upper right rontact 123 respectively and therefrom over the conductor 173 to ground at the armature of relay 11%. In other words, the relays 115 and 114 remain locked until sequenze switch 120leayes position 1% to open its upper right and lower left contacts 123. ilith relay 115 energized a circuit is established from battery through the winding of the magnet of sequence magnet switch 120, lower right and upper left contacts 137 (1), front contact of relay 115, lower right contact 172 (1+6) to ground. Sequence switch 120 advances out of position 1 and into position 2 and relays 115 and 114: become deenergized. Before the upper left contact 135 opens as sequence switch 120 passes out of position 1 the lower left contact 135 is closed in position 1% and the relay 117 remains energized in the fundan'iental circuit as follows: battery through the winding of relay 117, lower left contact 135 (1 |2), outer right contact of relay 117 and thence over the fundamental circuit as previously traced to ground at the left back contact of relay 112.

iiith relay 117 energized in position 2 of sequence switch 120 a circuit is completed from battery through the trip spindle power magnet 121, lower right contact 1&0 inner right front iontact of relay 117 to ground. The trip spindle magnet 121 rotates the trip spindle to select the proper set of brushes to be rendered active during the subsequent rotation of the brush carriage.

Upon leaving its normal position the trip spindle causes the interrupter brush 1 13 to more to disengage the con'iparatively deep notch thereby forcing it into contact with the interrupter spring 112. Although the spring 1 l3 encounters a notch at each brush tripping position the depth of this notch is not sufficient to permit said spring to disengage the spring 14:2. Conserpiently, springs 1&2 and 1&3 remain in contact with each other until the trip spindle again reaches normal. During the time that the trip spindle is rotated from one tripping position to another, the spring 143 is forced upwardly to a sufficient extent to cause spring 1.12 to engage the spri l-l-I, but when the tripping spindle is in one of its tripping positions the spring 143 falls into a shallow notch and permits the springs 1&1 and 1&2 to disengage.

While the tripping spindle is passing from one brush tripping position to another a circuit is closed as follows: From battery through the winding of relay 117, lower left ci'nitact 135 (1%+2), interrupter springs 14-1, 112 and 143 to ground. This circuit maintains the relay 117 energized and shunts out the stepping relay 102 in the fundamental circuit. The stepping relay 102 serves in the well-known manner to restore to its normal position the register which represents the amount of movement to be talren by the group selector switch 180 in selecting the proper set of brushes. The finiclaineutal circuit is opened by means of a relay 103 at the sender at the end of selection. As soon following the opening of the fundamental circuit at the sender as the tripping spindle reaches its next brush tripping position springs 141 and 142 become separated and the holding circuit of relay 117 is opened. Relay 117 becomes deenergized and in so doing severe the circuit of the trip spindle power magnet 121 whereby the trip spindle ceases to rotate. Moreover, relay 117 upon deenergizing closes a circuit from ground through its middle right back contact, lower right contact of spring 139 (2+4), winding of sequence switch magnet 120 to battery. Sequence switch 120 leaves position 2.

As sequence switch 120 reaches position 2% a circuit is closed from battery through the winding of relay 117, upper right contact 135 (2%+4), back contact of relay 118, lower left contact 134 (2+3%), back contact of relay 115,- lower right contact 172 (1+6) to ground. Relay 117 becomes energized and opens the circuit of sequence switch 120 permitting said sequence switch to stop in position 3. lVith sequence switch 7 120 in position 3 and the relay 117 operated a circuit is closed over the brush carriage power magnet 122 traceable from battery to the winding of said magnet, upper right contact 140 (3), inner right front contact of relay 117 to ground. The power magnet 122 operates to cause the brush carriage to rotate tripping the selected set of brushes and trailing the same over the terminals of the corresponding level in the contact bank.

Since the call. is one to a local subscribers line the level chosen by the group selector switch 180 contains the terminals of trunks which lead to local selector switches such as the switch 230. The first set of terminals 146, 147 and 148 in one of these local levels is left blank with the exception of the test terminal 148 which is wired as illustrated to the lower right contact 123, closed in position 3. Following this first set of terminals the succeeding sets of terminals such as sets 149, 150, 151 and 152, 153, 154, etc. represent local trunk lines.

When the tripped set of brushes 161, 162, 163 commences to rotate under the influence of the power magnet 122 they first encounter the terminals 146, 147, 148. A circuit is thereupon established from battery through the upper right contact 133 (1+12), lower left contact 133 (1+4), windings of relay 114. upper right contact 123 (3+4), lower right contact 123 terminal 148. brush 163, upper left contact 132 (3), left-hand winding of test relay 118 to ground. The resistance of the windings of relay 114 is such as to prevent the energization of relay 118 in the circuit traced. Relay 114, however, operates and locks in a circuit from battery as above traced through its windings to the upper right contact 123 (3+4) thence oyerconductor 173 to ground.

The brush carrlage continues to rotate and' thereafter the brushes 161, 162 and 163 engage terminals of trunk lines leading to the local selector switches. When a set of terminals representing an idle trunk 166, 167,168 is encountered a sufliciently high potential is found on the test terminal 151 to permit the cnergization of the test relay 118. The circuit for the energizationof this relay may be traced from battery through the winding of relay 203, and also in parallel from battery through contact 204 (1+10) of sequence switch 210, conductor 168, terminal 151, brush 163, upper left con tact 132 (3), left-hand winding of relay 118 to ground. Relay 118 becomes operated and opens the above traced circuit for rela. 117 which there-upon deenergizes and in turn opens the circuit of the power magnet 122. The brush carriage comes to rest with the brushes 161 162, 163 on the terminals 149, 150, 151 of the trunk 166, 167, 168. he lay 118 also closes a circuit over the test conductor through its right-hand lowv resistance winding and front contact, lower left contact 134 (2+3 back contact of relay 115, lower right contact 172 (1+6) to ground. Relay 118 thereby shunts out its left high resistance windingand in so doing reduces the potential on the test terminal 151 to such an extent as to render the selected trunk busy to other switches. )Vhen relay 117 becomes deenergized it closes the circuit from ground through its inner right back contact, lower right contact 139 (2+4), winding of sequence switch magnet 120 to ground. Sequence switch 120 leaves position 3 and moves into position 5. lVhen sequence switch 120 reaches position 3% the above traced holding circuit through the rigl'it-hand winding of relay 118 is modified so as now to extend to ground through upper right contact 134 (3%+ 16).

lVhile sequence switch 120 is passing through position 4 a. circuit is closed for the energization of relay 112 due to the fact that relay 114 is energized at this time. It will be observed that relay 114 is energized by reason of the fact that the selector switch 180 was operated to choose a group of trunks leading to local switches. A circuit for the energization of relay 112 may be traced from battery through the right-hand winding of said relay, upper left and lower right contacts 129 (4), left back contact of relay 117, conductor 174, lowerleft contact 12 3 (4), conductor 173 to ground at the contact of relay 114. Relay 112 becomes energized and closes a. circuit from battery through the winding of relay 116, up er right contact 127 (1%+13), left-hand winding and left front contact of relay 112 to ground. Relay 116 becomes energized and through the takes place and relay 112 remains energized in this circuit after sequence switch 110 has passed into position 5. The relay 112 by being energized at this time extends the fundamental circuit incoming over the trunk conductor 110, 111 directly through to the second local group selector switch 230 over an uninterrupted metallic path. Sequence switch 120 passes out of position 4 and the holding circuit of relay 1141 is opened and this relay becomes deenergized. In position 5 of sequence switch 120 a circuit is closed from battery winding of said sequence switch, lower right contact 138 (5+11), contact of relay 116, upper left contact 172 (3+13) to ground. Sequence switch 120 is energized in this circuit and moves over position 11 and into position 13.

The fundamental circuit is now closed through to the second selector switch 230 ready for controlling the selective movement of this switch. Said fundamental cir cuit may be traced from battery through the winding of relay 202, contact 200 (1+2), conductor 167, terminal 150, brush 162, left back contact of relay 113, middle right contact of relay 112, conductor 111, thence through the stepping relay 102 as previously traced and returning by way of conductor 110, upper contact 124k (1+13) innermost right contact of relay 112, brush 161, terminal 140, conductor 166 to ground at contact 201 (1+2). Relay 202 becomes energized and closes a circuit from battery through the winding of sequence switch magnet, 210, upper contact 212 (1), front contact of relay 202 to ground, driving said sequence switch out of position 1 and into position 2. In position 2 brush selection a circuit is closed for the brush tripping magnet 206 from battery through the winding of said magnet, left contact 229 (2), front contact of relay 202 to ground. The brush tripping spindle is rotated and for each brush tripping position a circuit is closed from battery through the winding of relay 202, contact 231, interrupter springs 207, 208 and 209 to ground. This circuit maintains the relay 202 operated and shunts out stepping relay 1020f the sender.

When the proper set of brushes have been selected the sender opens the fundamental circuit and immediately thereafter springs 207 and 208 become separated to open the substitute circuit for relay 202. Relay 202 deenergizes and opens the circuit of the trip spindle magnet 206. Relay 202 also closes a circuit from battery through the winding of sequence switch 210, upper contact 211 (2+3), back contact of relay 202 to ground. The sequence switch 210 is advanced from position 2 into position 5.

In position 5 the brush carriage power magnet 216 is energized in a circuit from battery through the winding of said magnet, lower contact 214: (5+6), back contact of test relay 215 to ground. The brush carriage is rotated to move the selected set of brushes 223, 22 1, 225 over the terminals of the contact bank in the trunk hunting operat-ion. When an idle trunk is found test brush 225 encounters a. high potential on the test. terminal 228 and the switch comes to rest. The test circuit may be traced from battery through the winding of relay 101, and also in parallel from battery through the contact 412, thence over terminal 228, brush 225, left contact 218 (5), right-hand high resistance winding of relay 205 to ground. The potential being high relay 205 is operated and immediately closes a circuit through its left-hand winding and contact and the winding of relay 215 to ground. This latter circuit is sufliciently low in resistance to reduce the potential on terminal 228 and its multiples whereby the final selector switch M0 is rendered nonselectable to other switches. Immediately after relay 215 is operated the circuit of the power magnet 216 is opened, stopping the brush carriage. Relay 215 also closes a circuit from battery through the winding of sequence switch magnet 210, upper contact 212 (5+7), front contact of relay 215 to ground. Sequence switch 210 moves out of position 5 over position 6 and into position 8. In position 8 the sequence switch 210 finds a circuit through the lower contact 212 and continues to advance into position 10. On reaching position 9 the test circuit leading from the linal selector switch through terminal 228 and brush 225 is now closed through the right contact 218 (9+ 15) and the winding of relay 215 to ground. This modified circuit shunts out the relay 205 permitting the same to become deenergized.

)Vhen the sequence switch 210 of the second group selector is in position 10 the fundamental circuit is completed for controlling the final selector switch 4A0. This circuit may be followed from battery through the winding of relay e00, left contact +122 (1+5), terminal 227, brush 22 1, lower cont act 219 (9+10), conductor 167, thence as previously traced through the stepping relay at the sender and returning by way of conductor 166,upper contact 220 (1.0), brush 223, terminal 226', left contact 421 to ground. Relay -l-00 now operates and closes a circuit from ground through its front contact, right contact 413 (l) winding of sequence switch magnet 110 to battery. Sequence switch 110 moves out of position 1 and into position 2. In this position the trip spindle magnet 403 is energized in a circuit from battery through the winding of said magnet. lower contact 131 (2). front contact of relay 400 to ground.

'10 102 at the sender. 'When the proper set or brushes has been reached the fundamental circuit is opened at the sender and shortly thereafter, when springs 406 and 407 are opened, the relay 400 becomes deenergized to open the circuit of the trip spindle magnet 405. Also, the relay 400 completes a circuit "from ground through its back contact, upper right contact 432 (2+5), winding 01 sequence switch 410 to battery. Sequence switch 410 leaves position 2. Be-

- tt'ore said sequence switch can reach position 5, however, the fundamental circuit as previously traced is again completed at the sender and relay 400 becomes energized to open the. driving circuit, of the sequence switch. Therefore, the sequence switch 410 stops in position where acircuit is closed for the power magnet 404. This circuit may be traced from battery through the winding of said-power magnet, lower contact 414 front contact of relay 400 to ground.

The power magnet 404 causes the brush carriage to rotate carrying the selected set of brushes 425, 426, 427'over the terminals of the selected level of called subscribers lines. interrupter springs 433, 434 are closed and a circuit is completed from battery through the winding of relay 400, lower contact 429 .10 2+5),springs 433 and 434 to ground. This c rcuit shunts outthe stepping relay 102 in.

the fundamental circuit and causes the restoration of the control register to its normal position. When the brushes of the final selector reach the terminals of the called subscribers line 430, the sender opens the fund-ament-al circuit and immediately thereafter springs 433 and 434 are separated to open the substitute circuit of relay 400. Relay 400 releases its armature, opens the circuit of the power magnet 404 and closes a circuit for driving sequence switch 410 out of. position This latter circuit is traceable from ground through the back contact of relay 400, upper right contact 432 (2+5).

7 the winding of sequence switch magnet 410 to battery.

Before proceeding with the testin' and Foreach set of terminals passed the circuit. This increase of resistance reduces the current to such an extent that relay 215 is unable to maintain its armature attracted. Relay 215 on releasing closes a-circuit from ground through its back contact,-upper con-' tact 214 (10), winding of sequence switch 210 to battery. Sequence switch 210 leaves position 10 and advances into position 15, which is the talking position of the sequence. switch. 7

As sequence switch 210 leaves position 10 the contact 204 is opened whereby the resistance in the test circuit extending back to the lirst group selector switch is also in-.. creased. In response to this increase of resistance the relay 11S releases its armature and a circuit is established from battery through the winding of sequence switch magnet 120, upper left contact 139 (13), back contact of relay 118, upper right con- 55 tact (3%4-16), to ground. Sequence switch 120 leaves position 13 and moves into position 14.

At this time, which is subsequent to the, completion of the final units selection, theta group selector 108, 109 having advanced to its talking position opens the lower left contacts 106, 107, and closes the upper left contacts 100, 107, the register sender 101 at the. originating otlice is therefore disassociated from the connection and a circuit established through from the calling subscribers line over trunk 110 and 111 in the usual manner. Consequently, if at the time the sequence, switch 120 reaches position 14, the calling SllbSClll'lOl' still has its receiver oil the switchhoo-k the relay- 114 is energized from a source of current at the group selector switch in the originating oliice. The circuit for relay 114 leads from battery at the upper left con- 10 tact 107 over the trunk conductor .111, middle right back .contact of relay 112, lower left contact 126 (13%-|-16), windings of relay 114, inductance coil 175, lower contact 124 (144-10), and thence over. the other side of trunk 110 to ground at the upper life contact 106. It will be noted that relay 112 and relay 116 become deenergized. as sequencc switch 120 left position 13. )Vith relay 114 operated a circuit is closed from battery through-the winding of relay 117. lower left contact 136 (144-16), contact of relay 114 to ground. Relay 1.17 becomes energized and closes a circuit from ground through its inner right front contact, lower left contact 139 (14-1-15), winding of sequence switch magnet 1.20 to battery. Sequence switch'120 moves from position 14 into position 16 which is the talking position thereof.

.lVhen relay 118 becomes d-eenergized as 195 sequence switch 210 leaves position 10 and until sequence switch arrives in position 15 the circuit of relay 203 is held opened. Relay 20?) is slow to release, however, and does not retract its armature during this in- 3 crs line and returning by way of brush 425,

terval. 'lVhen sequence switch 120 moves into position 15 relay 203 is maintained energized in a circuit 'leading'over the test conductor 168 and thence'through the upper left contact 132 (15-1-17) and the left-hand high resistance winding of relay 118 to ground. lVhensequence switch 120 later reaches position 16, the left-hand winding of relay 180 is shunted by the closure of the lower right contact 132. Hence, relay 203 remains energized and relay 118 remains deenergized.

In position 6' of sequence switch 110 a circuit is closed from battery through the winding of relay s00, lett contact 416 (6+7) to ground. Relay operates and closes a circuit from ground through its front contact, right contact e13 (6), winding of se quence switch magnet410 to battery, driving said sequence switch out of position 6 and into positionlO. As sequence switch 410 is passing through position 8 it closes a test circuit to testthe condition of the called subscribers line 430. The test circuit may be traced from the test terminal. 136, test brush 427, left-hand high resistance winding of rela}'"403,- right contact-416 (8) to ground.

Assuming the called line 430 to be idle, the

current flowing from battery through the winding of cut-off relay 128 of thetcst terminal 136 is sufficient to cause the energization of the test relay 403.- Relay-Ofloperates and closes a circuit through its righthand low resistance winding, armature contact, winding of relay'402, front contact of relay'401 to ground. This low resistance circuit reduces the potential on the multiples of test terminal 136, rendering tlie called line busy to other finalswitches. Relay 402 operates and closes a circuit from ground through the back contact of relay 400' (this relay having deenergized when sequence switch left position 7), front contact of relay' LOQ, lower right contact 432 (6-|-'11), winding of sequence switch -110 to battery. Thereafter sequence switch tlOcontinues to move through positions 10 and 11 and into position 12.

In position 12 a "circuit is closed from the ringing source I 419, right contact 418 (12+13) brush 126 over the called subscribupper contact 123 (12-l-14), Winding of relay 4.20 to battery.'-Ringmg current is "thereby innnediately applied to the called subscribers line. The relay 4120 being marginaldoes not operate at this time. Immediately afterthe sequence switch 410 enters position 12 a circuit is closed from battery through the winding of relay' 1-00, leftcontact 415 (12). to the brush of interrupter 437; lVhen this-*brusl-rcloses on a metallic I segment of the interrupter, relay 400 opermove out of position 13.

tact "413 (11-1-1-1), winding of sequence switch magnet 4-10 to battery. Sequence switch 410 moves out of position 12-and moves into position 13 where it comes to rest since the contact (12) opens the circuit of relay 400 before sequence switch 4-10 can At the end of a definite interval following the arrival of sequence switch 110 in position 13, a second interrupter 438 is closed to establish a circuit over contact 117 for relay 4-00. Relay 400 operates again and closes the circuit traced over sequence switch 410 which moves out of position 13 and into position 14. Inposition l-t the source of initial ringing current is disconnected and the ringing machine 439 is rendered effective to intermittently apply ringing current to the called line 430.

\Vhcn the called subscriber responds by removing his receiver from the switchhook, the resistance in the loop of his line'is so reduced that the marginal relay 4:20 becomes energized. Relay 4:20 closes a circuit by Way of contact 413 for driving sequence switch 410 out of position 11 and into position 15, which is the talking position. As sequence switch 410 reaches position 15 to establish the talking connection through the final selector and with the called subscribers receiver off the switchhook a circuit is closed for su iplying talking current to the called line from the first group selector switch 180. This circuit may be traced from battery through the winding of relay 116, lower right. contact 12? (16), outermost right contact of relay 112, left back contact of relay 113,-ln'ush 162, terminal 150, conductor 167. upper contact 219 (13-1-15), brush 22-1, terminal 227, upper contact 124 (15'). brush 1126, thence over the loop of the called line eti'lllybrush lower contact (15-1-17),

terminal 226, brush 223, lower contact 220 (13-1-15). conductor 166, terminal 1 1-9. brush -161, lower left contact 125 (16-1-17), im-

pedance coil 119, conductor 173, to ground at the contact of relay 11 1. Relay 116 operates and modifies the talking-circuit extending from the originating office by excluding the right-hand high resistance winding of relay 114;. The talking circuit 'fore, supplied through the left-hand wind ing ofrelay 114 and the impedance coil 175, while talking current for the called subscribers line is supplied from the'winding of relay 116 and the impedance coil 119. The

two branches of the talking circuit are separated by the condensers 176 and 177. Due to the exclusion of the right-hand high resistance winding of relay 114 at the response of the called subscriber, the resistance in the circuit leading back to the originating office is materially reduced and this principle may be utilized for any desired purpose such as controlling a message register or super visory signal.

At the termination of conversation the subscribers replace their receivers on the switchhooks and relays 114 and 116 and 117 become deenergized. Relay 117 closes a circuit from ground through its inner back contact, lower right contact 139 (16), winding of sequence switch magnet 120 to battery. Sequence switch 120 moves out of position 16 and into position 17. In position 17 a circuit is closed from battery through the winding of relay 117, upper right contact 135 (16 44-18), back contact of relay 118, lower right cont-act 134- (164-17), springs 142 and 143 to ground. Relay 117 operates and closes a circuit from battery through the trip spindle power magnet 121. lower right contact 140 ('17), inner front contact of relay 117 to ground. The trip spindle is rotated back to its normal position where the interrupter spring 143 enters the deep notch and causes its separation from spring 142. Relay 117 thereupon becomes deenergized and opens the circuit of the magnet 121 and also closes a circuit from ground through its inner right back contact, lower left contact 129 (17 +18), upper right contact 129 (16-I-17). inner right back contact of relay 113. winding of sequence switch magnet 120 to battery. Sequence switch 120 moves into position 18 where the brush carriage is restored to its normal condition. Relay 117 is operated in a circuit from battery through the winding thereof, upper right contact 135 (16%+18), left back contact of relay 118, upper right contact 134 (17%4-18) to ground. Relay 117 closes'a circuit from battery through the brush carriage power magnet 122, upper right contact 140 (18), inner right front contact of relay 117 to ground. When the brush carriage has been. fully restored a circuit is closed from battery through the home contact 165, brush 164, upper right contact (174-18 1,), left-hand winding of relay 118 to ground. Relay 118 attracts its armature and opens the circuit of relay 117which in turn deenergizes and opens the circuit of the brush carriage power magnet 122. Relay 117 also closes a circuit from ground through its inner right back contact, lower right contact 139 (18), winding ofsequence switch magnet 120 to battery, driving said sequence switch into its normal position, 1.

Sequence switch 120 on leaving position 17 opens at its contact 132 the holding cirletes a circuit from ground through con-,

tact 213 (10+16), winding of sequence switch 210 to battery. Sequence switch 210 moves out of position 15 and into position 17. In position 17 the brush carriage, is

restored to its normal position by means of a circuit from battery through the power magnet 216, lower contact 214 (17), back contact of relay 215 to ground. When the brush carriage is fully restored, a circuit is closed from battery through the contact 217 (164-18), home contact 222, brush 221,

Relay 215- winding of relay 215 to ground. operates and opens the circuit of the power magnet and closes a circuit from ground throughits'front contact, upper contact 212 (15+18), winding of sequence switch magnet 210 to battery. thereupon moves into position 1. It will be noted that the trip spindle of the second group selector switchrestores to its normal position as soon as the sequence switch 210 reaches position 8. its restoration is traceable from battery through the n'iagnet 206, right contact 220 (8+1), interrupter springs 208 and 209 to ground.

Sequence switch 210 on leaving position 15 opens the holding circuit of relay 401. This relay becomes deenergized and com pletes a circuit from ground through its back contact, upper contact 409 (12+16), winding of sequence switch magnet 410 to battery. Sequence switch 410 advances out of position 15 and into position 17. In position 17 a circuit is closed .fron battery through the winding of sequence switch magnet 410, upper right contact 432 (17). back contact of relay '400 to ground and sequence switch 410 moves into position 18.

The brush carriage is now restored to its normal condition by means of a circuit from battery through the winding of power magnet 404, upper contact 414 (18), back con tact of relay'402', back contact of relay 400 to ground. hen the brush carriage reaches normal a circuit is closed from battery through the winding of relay 400, right contact 415 (18), and brush 435 to ground. Relay 400 operates and opens the circuit of the power magnet 404, stopping the brush carriage. Relay 400 also closes a circuit from ground though its front contact, right contact 413 (18), winding of sequence switch 410 to battery, driving said sequence switch into its normal position, position 1. It will be noted that the trip spindle of the final selector restores to normal as soon as sequencevswitch 410 reaches position 12 over a circuit from battery through the magnet 405, upper contact 431 (12+1), in,- terrupter springs 407, 408'to ground. All apparatus taken in connection with estab- Sequence switch 210:

The circuit for causing lishment of a call from the subscribers line 100 to the subscribers line 4:30 local to the second exchange has thus been re stored to its normal condition.

Establisimzmit of a call to a distant ofiice.

Consideration will next be given to the establishment of a connection from the calling subscribers line 100 to a called subscribers line 130 which terminates 1n an oflice distant from the ofiice containing the group selector 180. In this case the selector switch 180 chooses an outgoing two-Wire trunk leading to the distant called office and there terminating in a group selector switch 330.

The initial operations following the registration of the call proceed in substantially the same manner as already discussed heretofore, the register sender 101, however, taking a somewhat different setting in View of the fact that a call of a different class is being made. Following the setting of the sender the group selector 108, 109 is positioned and an idle trunk 110, 111 leading to the second or tandem oflice is chosen. Thereafter the fundamental circuit is prepared as above explained and the group selector switch 180 is operated in its brush tripping movement to select a set of brushes having access to a level of trunks outgoing to the distant called oliice. These trunks are indicated by the terminals 155, 156, 157, 158, 159, 160, etc. It will be recalled that following the brush tripping movement of the switch 180 the sequence switch 120 advances from position 2 into position 3. In position 3 of the sequence switch the circuit already traced is closed for the power magnet 122 and the brush carriage commences to rotate advancing the tripped set of brushes 161, 162 and 163 over the terminals of the trunks leading to the distant office.

This time the first set of terminals in the level represent an outgoing trunk instead of being used for adiscriminatory purpose as in the case of a level of local trunks. There fore, the circuit previously traced for the relay 114 is now held open when the test brush 163 encounters the first test terminal in the level inasmuch as this terminal is connected to battery rather than being connected to the sequence switch contact 123. The brush carriage continues to rotate until the terminals of an idle trunk are reached, at which time a high potential is encountered by the test brush 163. A circuit is then closed from battery over test terminal 160, brush 163, upper left contact 132 (3), winding of relay 118 to ground. Relay 118 operates and closes a low resistance circuit through its righthand winding and contact 134 to ground. The low resistance of the right-hand winding of relay 118 reduces the potential on ter minal 160, rendering the trunk non-selectable to other switches. Relay 118 also opens the circuit of relay 117 which in turnopens the power circuit causing the switch to come to rest. Relay 117 moves the sequence switch out of position 3 and into position 5.

lvhile sequence switch 120 is passing through position 4 the circuit hereinbefore traced for relay 112 is held open due to the fact that relay 114 did not operate at the time the brushes of the switch passed over the first set of terminals in the level. Consequently, on an interoliice call both the relays 112 and 116 remain deenergized.

The fundamental circuit over which the sender 101 controls the selector switch 330 in the distant office is prepared in two sections with provision for repeating the impulses from one section of the circuit to the other. )Vith sequence switch 120 in position 5 a circuit is closed from battery through the winding of relay 117, upper left contact 135 (5), middle right back contact of relay 112 thence over the conductor 111, through the winding of stepping relay 102 and returning over conductor 110, upper contact 121 (1+13), upper left contact 128 (5+7), leftback contact of relay 112 to ground. Relay 117 operates and locks in a circuit from battery through its winding, lower left contact 135 (5+13), outer right contact of relay 117 and thence as previously traced over the circuit including the stepping relay 102 to ground on the left contact of relay 112. Relay 117 on operating closes a circuit from battery through its inner right front contact, lower left contact 139 (5), winding of sequence switch magnet 120 to battery, driving said sequence switch into position 7. Relay 117 remains locked in the circuit traced in position 7 of the sequence switch. The fundamental circuit interconnecting the switch 330 in the distant ofiice and the switch 180 is established as follows: battery through the winding of relay 300, lower left contact 31d (1+1 fi conductor 170, terminal 159, brush 162, left back contact of relay 113, outer right contact of relay 112, upper left contact 130 (ti +7), lower left contact 130 (1+17), winding of relay 115, conductor 178, left front cont-act of re lay 117, conductor 179, upper right contact 125 (6%+7), brush 161, terminal 158, conductor 169, left contact 318 (1+2) to ground. Relay 300 becomes operated in this circuit and completes a circuit from ground through its right front contact, lower left contact 312 (1), upper right contact 312 (1+6), left-liand'winding of relay 303, lower left contact 315 (1), left-hand winding of relay 301, lower left contact 321 (1), upper right contact 321 (1+4) to battery. Relays 301 and 303 attract their armatures and a circuit is closed from battery through the winding of sequence switch magnet 310, upper left contact 311 front contact of relay; 303,, right contact 318' (17%+1) to ground. Sequence switch 310 moves out of position 1 and into position 2 and relays 303 and 301 become de'energized. Relay 300 remains energized in position 2 of the sequence switch by means of a circuit from battery through its winding and left contact, conductor 331, lower right contact 322 (1%+2) thence over the fundamental circuit as previously traced to ground.

The brush tripping magnet 304 is now energized by means of a circuit from battery through the winding of said magnet, lower left contact 332 (2), right front contact of relay 300 to ground. For each tripping position passed over by the spindle a circuit is closed from battery through the winding of relay 300, left contact of said relay, interrupter springs 306, 307 and 308 to ground.

This circuit maintainsthe energization of relay 300, but causes the relay 115 in the other end of the fundamental circuit to be shunted. Relay 115 -upon deenergizing closes a circuit, from battery through the winding; of relay 117, lower right contact 136 (7) back contact of relay 115, lower left con tact 140. (7), inner right front contact of relay 117 toground. This circuit maintains the energization of relay 117, but shuntsout the steppingrelay 102 at the sender 101. The stepping relay 102' in the well-known Vmanner'causes the advance of the corresponding register. .This procedure continues, relay being shuntedfor each tripping position passed over by the trip spindle of the switch 330 and in turn causing the shunting of relay 102 at the sender until the proper set of brushes has been selected. At this timethe fundamental circuit is opened at the sender. As soon, following the opening of the fundamental circuit at the register sender in the originating office, as the interrupter springs 306 and 307 are opened the relay 115 becomes energized and in so doing opens the substitute holding circuit of relay 117. Relay 1 17 thereupon retracts its armatures and in turn opens the circuit including relays 115 and 300. These relays become deenergized and relay 300 by retracting its arniatures opens the circuit of .the trip spindle magnet 304, Relay 300 also closes a circuit from ground through its right back contact, lower left contact 311 (2+4). winding of sequence switch n'iagnet 310 to battery, Sequence switch 310 leaves position 2 and on reaching position 3 a circuit is closed from battery through the winding of relay 300, upper right contact 314 (2+5), back contact of relay 303, back contact of relay 302, upper right contact 317 (2 +9}, lower right contact 317 (2+4), interrupter springs 307 and 308 to ground. Relay 300 operates and opens the circuit of sequence switch 310causing the same to stop in position 3. s i

selector busy to other switches.

tion of the brush tripping operation ac r cuit is closed from ground through the inner right back contact of said relay, lower right contact 139 (7), Winding of sequence switch 120 to battery. Sequenceswitch 120 moves out of position 7 into position 8 where it remains until the switches are in condition for the next selective operation. Vith sequence switch. 310 in position 3 a circuit is closed from battery through the winding of relay 300, upper right contact 314 (2+5), back contact of relay 303, back contact of relay 302, upper right contact 317 (2%3-9), lower right contact'317 (2+4), springs307 and 308 to ground. Relay 300 completes a circuit from battery through the winding of hrushcarriage power magnet 305, lower right contact 332 3), rightfront contact'of relay 300 to ground. The selected set of brushes 323, 324 and 325 are driven over the terminals of the bankin the trunk hunting 7 movement When an idle I switch is found a circuit is closed from batter alsii in parallel from'battery through contact 412, test conductor 328, brush 325, up per right contact 315 (3), right-hand high resistance winding of relay 303 to ground. Due to the presence of a high potential in this circuit test relay 303 is operated and opens the circuit of relay300 which in turn deenergizes and opens the circuit of the power magnet 305. Relay 300 moreover completes a circuit. from ground through its right back contact, lower left contact 311 (2+4), winding of sequence switch magnet 310 to battery, driving said sequence switch out of position 3 and into position 5. lay 303 on operating closes the circuit over the test conductor through its le ft-hand low resistance winding, upper right contact 312 (1+6), upper left contact 312 (3+6), frontcontact of relay 303 thence to ground as'previously traced throughinterrupter springs 307 and 308. This low resistance circuit reduces the potentialon terminals of the trunk the final selector to render said Assoon as sequence switch 310 reaches position 3% the circuit of relay 303 is modifiedto extend to ground at the right contact 318 (3 +8).

The fundamental circuit is now prepared for controlling the brush tripping operation of the final selector switch. hen sequence leading to final selector switch 310 is in position 5 a circuit is closed from battery through the winding of relay 400, left contact 422 (1+5), conductor 328, brush'324, upper right contact 320 (5+9), lower left contact 320 (5), conductor 170, terminal 159, brush 162, left back contact of relay 113, outermost right contact of relay 112, lower right contact .126 (8+9). W n 7 j 13 ings, of relay 114, impedance coil 175, upper left contact (8+8 brush 161, terminal 158, conductor 169, upper left contact 319 (5+9), upper right contact 319 (5), brush 323, conductor 326, left contact 421 (1+5) to ground. Relay 114 operates in this circuit but due to the high resistance of the right-hand winding of relay 114, relay 400 does not receive sufficient current to energize. As soon as the sender 101 is in condition to control the next selective movement, a circuit is established from battery through the winding of relay 117, upper left contact 135 (8), middle right contact of relay 112 over the conductor 111 through the winding of the stepping relay 102 returning by wa of conductor 110, upper right contact 124 (1-I-13), lower right contact 128 (8+9) to ground at the contact of relay 114. Relay 117 completes a circuit from ground through its inner right front contact, lower left contact 139 (8), winding of sequence switch 120 to battery. Sequence switch 120 moves out of position 8 and into position 10. Relay 117 remains energized in position 10 in a locking circuit traceable from battery through the winding of said relay, lower left contact 135 (5-1-13), outer right contact of relay 117, thence over the fundamental circuit as previously traced returning by way of conductor 110, upper right contact 124 (1-l-13), upper left contact 128 (8%+10) to ground at the left back contact of relay 112. When sequence switch 120 moves out of position 8 and into position 9, relay 114 becomes deenergized but this relay does not release until after the upper left contact 128 is closed. With sequence switch 120 in position 10 and with relay 117 energized a circuit is now established from battery through the winding of relay 400 at the final selector switch thence as previously traced over the lower talking conductor to brush 162, left-hand contact of relay 113, outermost right contact of relay 112, upper left contact 130 (9 +1O), lower left contact 130 (1-1-17), winding of relay 115, conductor 178, left front contact of relay 117, conductor 179, upper right contact 125 (9 440), brush 161, thence over the upper talking conductor to ground at contact 421. Due to the low resistance of relay 115, the relay 400 at the final switch becomes energized. Relay 400 causes the advance of the sequence switch 410 into position 2 where the brush tripping spindle is operated in the manner hereinbefore explained.

At each brush tripping movement of the switch the relay 115 is shunted and this relay in turn causes the shunting of relay 102 at the sender 101. When the proper set of brushes have been reached in the operation of the final selector, the sender opens the fundamental circuit and shortly thereafter relays 117, 115 and 400 become deenerv gized, Relay 400 advances the sequence switch 410 into position 5, while relay 117 completes a circuit as follows: ground through the inner right back contact of relay 117, lower right contact 139 (10), winding of sequence switch magnet 120 to battery. Sequence switch 120 moves out of position 10 into position 11.

Immediately after sequence switch 120 reaches position 11 a circuit hereinbefore traced is closed including relay 400 at the final switch and relay 114 at the group selector 180. Relay 114 operates but relay 400 remains deenergized. Relay 114 closes the cir-- cuit above traced for relay 117 including the stepping relay 102 of the sender. Relay 117 closes a circuit through its inner right front contact and the lower left contact 139 (11) for driving sequence switch 120 into position 13. In position 13, the relay 117 I remains energized in the locking circuit as previously traced through the lower left contact 135 (5-1-13) and the outer right contact of relay 117. As soon as sequence switch 120 reaches position 12 on its way to position 13 a circuit is closed from battery through the winding of relay 400 thence over the lower talking conductor hereinbefore traced, left back contact of relay 113, outermost back contact of relay 112, upper left contact 130 (12 4-13), lower left contact 130 (1+17), winding of relay 115, conductor 178, left contact of relay 117, conductor 17 9, upper right contact 125 (12 5-?- 13), thence to ground at contact 421. The closure of this circuit occurs before sequence switch 410 has time to reach position 5 and hence relay 400 becomes operated to open the driving circuit of the sequence switch permitting it to stop in said position. The units selecting operation now takes place at the final switch at the end of which the fundamental circuit is opened and relays 115, 117' and 400 become deenergized. Relay 117 closes the circuit from ground through its inner right back contact, lower right contact 139 (13), winding of sequence switch magnet 120 to battery driving said sequence switch out of position 13 into position 14.

Immediately following the units selecting operation the register sender 101 is detached and a source of battery current at the group selector switch at said originating office is connected to the outgoing trunk line 110, 111 provided the calling subscriber has not replaced his receiver on the switchhook. The relay 114 is connected across the trunk 110, 111 as previously explained and energizes in series with the battery source at the originating office. Relay 114 closes a circuit from ground through its contact. lower left contact 136 (14-1-16), winding of relay 117 to battery. Relay 117 completes a circuit from ground through its inner right front contact, lower left contact 139 (RH-15), winding oi -sequence switch mag net 120 "to' battery driving sa-id-sequence switch into position 165 )Vhen sequence switch %110 of the final Selectonmoves out of position 5, contact 12 is opened and hence the-resistance in series with the test circuit is increased." =Thi's' increase of'resistancecauses the relay 303 to be deenergized, relay- 4:01 remaining operated. Relay 303 on retracting its armature completes a circuit from battery through the winding of relay 300, upper right contact 314 back contact of relay-303 right contact 318 (3 -l-8) to ground. Belay 300 "operates and closes a circuit from ground through its right'front contact, upper right contact 311 (5+8); winding'iof the sequence switch magnet-310m battery. Sequence switch 310 leaves position -5 "and moves into position 7. Since thewcalling subscriber still i has" his receiver off" the switchho'ok relay 1114 is energized and-consequently relay 117 is energized and-sequence sWitch 12O- standing in. position 16. Hence, when sequence switch 310 re'aches-position:6 a circuit is closed from batte'ry'through the winding of relay 116,

lower right contact 127 (16), outer-most right contact of relay 112 left contact of relay 113, b-1ush 162,' ter1ninal-159, conductor 170 upper left 'contact322 (6+9),

through the 'windings of relay 301,. lower right contact 321 (6+9), upper left contact 321 (6+9), conductor 169, terminal' 158, bruslr 161-, lower left contact 125 (16+17), impedance coil 119', conductor 173 to ground-at the contact of relay 114. Relay 301 operates and closes a circuit from battery'- through the winding of relay 300, lower right contact 313 (6+9) to ground at the contact of relay 301. Relay 300,'tl18I'B-r fore, remains energized and holds the circuit of-sequence switch 310 closed whereby said sequence switch moves over positions 7 and'8 and into position 9. ,Relay 300. remains energized in position 9 of the sequence switch. As sequence switch 310 enters posit-ion 6 the circuit of relay 4:01'is extended by Way of'conductor 327 directly to ground (6+9) there'- by shunting out the test relay 303. 7

Following this the final selector switch tests the -called subscribers line,- applies ringing currentthereto if same is idle and.

r the circuit is finally prepared .for talking WVhenthe called subscribe-r answers a cir cuit is closed from battery through the winding of relay 302, lower right contact 320 brush324'and thence overthe loop of the called subscribers line-430 "and returning to brush 323,- impedanoe coil 309, upper right contact 352 (EH-10) to ground atthe right front contact of relay- 300. Relay 302 becomes energized and shunts out the upp r right" contact 320 (5+9),

tact- -322 =*(6l 9), deft-hantl winding of rey la 301-,"upper le-t't contact 317 (SH- 1 0) upper. right contact-r317:v(2%+'9)- front con tact oil 2 relay: 302; lower right and upper left contacts 1321i 6+9) and thence: zover COIlClUCtOF 169. I1 Rela'y 116: which w'asincluded in serie's witlr the high-' resistance winding of relay 301 doe'snot operateiuntil said if highs resistance winding is: removed froniithehcircu'it at the response-rot the calledsubscriber; Relay 116' now attracts its armature and'iniso doing shuntszout-xthe right-hand 7' high resistance 1. winding of. re;- lay 11 i excluding the same from the circuit leading backto' the originating ofiice. This decrease :inJi-the resistance may: be

utilized as heretofore-observed'for supervision-or for line registration or forany other desiredipurpose. i. V Atthe endof con'versation the subscrib ers.v replace their IQCBiVSI'Sz OIl? the switchhooks and 'rrelays 114;,and-302 becorne 'deenergized. Relay l liopens thecircuit of relay; 117; which in turn closes the circuit for driving sequence switch 120-v into position 17. Thereafter: the restoration}- of the group selector switch '180 is substantially the same: as ab'ovedescribed. hen sequence switch 120' leaves I position 16 relay 301 at thedistant ofiice becomes deenergized-nand in so doingropens a circuit of relay- 300. Relay 300i completes-a circuit from groundzpthrough.its; right back contact, lower deft contact 311 (SH-18), winding .of sequence switch magnet310to battery. vSequenceswitch 310 leaves posi-v tion9. Onreacliin'gp'osition15% a circuit is, closed from battery through the winding of relay 300, upper right contact 314 (15+ 18) backcontact of relay 303; back'contact of relay "302; upper right contact 317 (15 +16)- lower right contact 317 711+ 16), springs307and 308 to ground. Relay 300 opens the circuit of sequence switch 310 which stops in'position 16; Here acircuit is closed from battery through. theitrip spindle magnet 304, lower left contact 332 (16), front contact of relay 300 to ground. The trip spindle restores and on reaching normal the circuit ofrelay 300 is opened by springs 307 .and'308. Relay 300 opens the circuit of magnet 304. Relay 300 also closes a circuiteincluding the lower left contact 311 for driving sequence switch 310 out of stop in position 18. The brush carriage restores in this position by means oi. a circuit from battery through the winding of power magnet 303, lower right contact 332 (18 rightiiront contact of relay 300 to ground. When the brush carriage reaches its normal position a circuit is closed "from battery through the brush 333, upper lefthand contact 316 (lit-18%,), lower left contact 316 (10-1-8), right-hand winding of relay 303 to ground. Relay 303 operates and opens the circuit of relay 300 and this relay becomes deenergized and opens the circuit of the power magnet 305. Relay 300 also closes a circuit from ground through its right back contact, lower left contact 311 (9+18), winding of sequence switch 310 to battery, driving said sequence switch out of position 18 and into position 1.

The restoration of the final selector switch shown in Fig. at takes place in substantially the same manner as previously discussed.

hat is claimed is:

1. In a telephone exchange system, a plurality of calling lines, a plurality of trunk lines of different classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, an automatic switch for further extending said connection, a sender common to said plurality of calling lines, a control circuit including the selected trunk for controlling said automatic switch, and means rendered effective by said selective switch according to the class of the trunk selected for determining the character of said con trol circuit.

2. In a telephone exchange system, a plurality of calling lines, a plurality of trunk lines of different classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, an automatic switch for further extending said connection, a sender common to said plurality of calling lines, a control circuit including the selected trunk, means controlled by said sender over the control circuit for operating said automatic switch, and means rendered effective by said selective switch according to the class of the trunkselected for determining the character of said control circuit.

3. In a telephone exchange system, a plurality of calling lines, a plurality of trunk lines of different classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, an automatic switch for further extending said connection, a sender common to said plurality of calling lines, a control circuit including the selected trunk for controlling the operation of said automatic switch, and means individual to the selective switch rendered effective by such switch according to the class of the trunk selected for determining the character of said control circuit.

a In a telephone system, a plurality 0t trunk lines of different classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, automatic switches, one in which each of said trunks terminates, means for operating said automatic switches to further extend a connection, a control circuit including the selected trunk for controlling the corresponding automatic switch, and means rendered effective by said selective switch in its operation of selecting a trunk of any class for determining the character of the control circuit.

5. In a telephone exchange system, a plurality of calling lines, a plurality of trunk lines of difi'erent classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, an automatic switch for further extending said connection, a sender common to said plurality of calling lines, a control circuit extending from the sender to said automatic switch and including the selected trunk for controlling the movement of said automatic switch, a repeater, and means rendered efiective by said selective switch in its selective operation for inserting said repeater in the control circuit.

6. In a telephone exchange system, a plurality of calling lines, a plurality of trunk lines of difierent classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, an automatic switch for further extending said connection, a sender common to said plurality of calling lines, a control circuit extending from the sender to said automatic switch and including the selected trunk for controlling the movement of said automatic switch, a repeater individual to the selective switch, and means rendered effective by said selective switch in its selec tive operation for inserting said repeater in the control circuit.

7. In a telephone exchange system, a plurality of calling lines, a plurality of trunk lines of difl'erent classes, a selective switch, means for operating said switch to select one of said trunks to extend a connection thereover, an automatic switch for further extending said connection, a sender common to said plurality of calling lines, a control circuit extending from said sender to the automatic switch and including the selected trunk, means for sending impulses over the control circuit for determining the operation of the automatic switch, and means rendered effective by the selective switch in its operation for repeating the impulses sent over said control circuit when a trunk of a certain class is selected.

8. In a telephone exchange system, a trunk line. of a given c1ass, a second trunk line of a difie rent cla ss, a selective switch, means for operating said switch toselect either of said trunks to extend a connection thereover,

automatic switches, one in which each of said trunks terminates, a sender, a control circuit extending from the sender to the cor: responding automatic switch when a connection iscexitend'ed over'said first trunk, means for sending impulses over said control circuit between the automatic switch and the sender for determining the movement of such automatic switch, a second-control circuit extending between the other automatic switch and the sender when a connection is LIPA POLINKOVSKY' 

